2003IAUC.8131....2O

M. Orio, Italian National Institute for Astrophysics at Turin, and University of Wisconsin; E. Leibowitz, Tel Aviv University; and P. Rodriguez, European Space Agency, report (on behalf of a team including V. Burwitz, R. Gonzalez-Riestra, Y. Lipkin, J. U. Ness, S. Starrfield, and M. Still) that V4743 Sgr was observed as a target-of-opportunity with the XMM-Newton satellite beginning on Apr. 4.921 UT for about 10 hr: "The EPIC-pn count rate in 'timing mode' was 1348.0 ± 0.3 counts/s in the range 0.2-10 keV. The average absorbed flux the range 0.2-2 keV was about 1.5 x 10**-9 erg cm**-2 s**-1, as high as was observed in the first half of the previous x-ray observation with Chandra (IAUC 8107). The spectrum was extremely soft with absorption features, which we attribute to the central white-dwarf atmosphere. Preliminary results from the lightcurve analysis reveal that the peak in the power spectrum reported on IAUC 8107 is now resolved into two separate peaks, P_1 = 1309.5 s and Q_2 = 1375 s. The first overtone of P_1 is also present in the power spectrum. The period Q_2 seems to be the first overtone of a fundamental periodicity, P_2 = 2746 s, that appears significantly in the power spectrum, although with much smaller power. A third period, P_3 = 1656 s, is probably also present. Despite variability by up to about 20 pecent, the x-ray flux never decreased to the level observed at the end of the recent Chandra observation (IAUC 8107). If an eclipse caused the obscuration observed with Chandra, the orbital period must be longer than 10 hr. We urge optical photometry to detect the orbital period, in order to understand the mechanism that obscured the strongest x-ray source in Mar. 2003."